Cnooc Ltd. has  agreed to acquire Canadian oil sands company Opti Canada Inc. for $2.1 billion in cash and debt, a move that will give China's third-largest national oil company a 35 percent stake in the Long Lake oil sands project located in the Athabasca region of northeastern Alberta.

The deal comes a week after Opti Canada filed for creditor protection under Companies' Creditors Arrangement Act (CCAA) as it ran out of cash to fund its oil sands operations.

Cnooc would pay $34 million, or 12 cents a share, to Opti Canada's common shareholders, $1.18 billion for some notes and assume $825 million of debt.

The access to Long Lake oil sands project comes at a time when Chinese oil majors are expanding outside in search of additional resources.

The Long Lake oil sands project, which is owned 65 percent by Nexen, is expected to have through-put rates of about 72,000 barrels per day of bitumen at full production.

It is anticipated that the Long Lake Upgrader will ultimately produce approximately 58,500 barrels per day of products, primarily Premium Sweet Crude -- a product that does not need to be diluted to transport in pipelines and fetches a higher price at refineries.

Cnooc, which had 2010 current production of approximately 901 million barrel of oil equivalent a day (Mboe/d), would get three other projects in Alberta.

Opti Canada's working interest share, before royalties, of raw bitumen reserves and resources on its oil sands leases is estimated to be 195 million barrels of proved reserves, 534 million barrels of probable reserves, 1,100 million barrels of contingent resources and 335 million barrels of prospective resources.

These reserves and resources are estimated to be sufficient to support about 430,000 barrels per day of bitumen production, Cnooc said..

The deal, which is subject to customary regulatory and shareholder approvals, is expected to close in the fourth quarter of 2011. Meanwhile, over 55 percent of second lien noteholders have agreed to vote in favor of the deal.

We are pleased to expand our presence in the oil sands business after our successful investment in MEG, Yang Hua, Chief Executive of Cnooc said in a statement.

We look forward to working with our new partner Nexen, to optimize value from the Long Lake Project and the three other jointly owned oil sands leases Li Fanrong, President of Cnooc said.

ADRs of Cnooc closed Tuesday's regular trading session at $234.81. In the pre-market, they fell 3.71 percent to $226.09.